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Title: The Atchafalaya River Delta. Report 4, Generic analysis of delta development
Authors: Louisiana State University (Baton Rouge, La.). Coastal Studies Institute
United States. Army. Corps of Engineers. New Orleans District
Wells, John T.
Chinburg, Susan J.
Coleman, James M.
Keywords: Atchafalaya River (La.)
Delta development
Sediment transport
Alluvial plains
Publisher: Hydraulics Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; HL-82-15 rept. 4.
Description: Technical Report
Abstract: The development of two freshwater deltas in Atchafalaya Bay is providing new subaerial land in south-central Louisiana in an area traditionally subjected to coastal retreat. From the engineering and scientific standpoints, it is important to know at Hhat rate and by what mechanisms the deltas in Atchafalaya Bay will continue to grow. Utilizing maps, charts, aerial photographs and published and unpublished literature, growth patterns in 10 similar deltas and subdeltas were examined as a means of projecting the rate of growth and configuration of subaerial land in Atchafalaya Bay to the year 2030. Results indicate that total subaerial land in Atchafalaya Bay will range from 150 km² to 337 km² with 208 km² representing the expected land in 50 years under average flood regimes. Subaerial land will emerge on the open shelf before the bay reaches a sediment-filled state. Persistent scour channels, slow sedimentation in distal areas, reworking of sediments during passage of cold fronts, subsidence, and selective natural sealing of the sediment delivery network will ensure that large areas of the bay will always remain open. The subaerial deltas will continue to grow as lobate additions of land caused by the processes of channel extension, channel bifurcation, and lobe fusion. Within 50 years the hundreds of small lobes will have fused into perhaps 10 major lobes separated by small dying channels. Approximately 14 x 10^6 m³ of sediment per year is retained in Atchafalaya Bay. Subaerial land that is lost during years of low river discharge resides in the shallow subaqueous environment and provides a platform for future subaerial growth. As the deltas prograde onto the shelf, waves and wind-driven currents will become more important in shaping the delta lobes. Strong southeasterly currents following the passage of cold fronts will tend to skew the sandy components to the southeast, thus fractionating them from the silts and clays that will be carried west in the predominant coastal drift system.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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